Present invention relates to a pneumatic tire having a structure of a semi-radial tire. The invention also relates to a pneumatic tire suitable for achieving maneuverabilities at high speed, such as turning maneuverability, braking performance and straight-traveling performance. The invention relates, for example, to a tire for a four-wheel car such as racing car.
Semi-radial tires (bias belted tires) are occasionally used in order to achieve merits of both of radial and bias tires. Meanwhile, to cope with requirements of high maneuverability at high speed, investigated are improving of structures of the carcass and belt layers of pneumatic tire and arranging of a reinforcing layer.
According to a tire proposed in JP2008-024063A (Japan patent application publication No. 2008-024063), two carcass plies are overlaid with each other to form a carcass layer, in which each cord of one ply is inclined reversely to that of another ply, and a reinforcing layer is arranged on inner-face side of the tire. In this tire, one carcass ply, which is wound around a tire bead portion prior to the other, extends up to a position well within outer face of the tire bead portion; and the other carcass ply extends up to a middle height of a sidewall of the tire. Moreover, the reinforcing layer is arranged in a region starting from a position well within inner face of the tire bead portion and reaching shoulder portion of the tire. In other words, the reinforcing layer is arranged in a region for exhibiting flexibility of the tire. It is asserted, in JP2008-024063A, that such construction improves maneuvering stability.
According to a tire proposed in JP2007-290578A, in order to improve “traction and side-grip performances”, arranged are two carcass plies and three reinforcing layers wound around the tire bead portion. JP2007-290578A also shows a tire, in which turned-up end of one carcass ply reaches a position inner than a fringe of the belt layer (FIG. 2, “ultra-high turned up construction”).
According to a tire proposed in JP2011-000958A, in order to “enhance maneuverability of the tire without impairing comfortable ride”; “each cord of one carcass ply intersects that of another carcass ply to forma biased part and is inclined in opposite directions” between tire's side faces respectively coming to inner and outer sides of the of the vehicle, so as to form a symmetrical tire. JP2011-000958A also shows a tire, in which the carcass plies arranged “as omitted in a center region as separated to two regions as distant in tire-width direction”.